         ([] (rf))
         ([result] (rf result))
         ([result input]
-         (rf result [(vswap! sum delta/add input) input]))))))
+         (rf result [[:is (vswap! sum delta/add input)] input]))))))
 
 (def ^:private first-then-second
   (fn [rf]

              chs {}]
      (let [[msg port] (alts! [subscribe-ch
                               cancel-ch])]
        (case port
          subscribe-ch
          (let [[this identifier target] msg
                [m :as cache]


(defn compscriber
  [service]
  (let [service (-> service
                    (compscribe-service)
                    (hybrid-cache))
        compile-spec (memoize compile-spec)]
    (reify
      IStream
